Revert "docker: Install qemu-user-static 6.0 to fix segfault"

This reverts commit 91af617bea.

qemu is no longer in experimental so the container build
will now fail. The required patches for qemu have been
backported into bullseye so let's revert using qemu from
experimental.

Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=988174
Signed-off-by: Christopher Obbard <chris.obbard@collabora.com>

docker/Dockerfile

@@ -56,8 +56,7 @@ LABEL org.label-schema.docker.cmd 'docker run \
 
 # debos runtime dependencies
 # ca-certificates is required to validate HTTPS certificates when getting debootstrap release file
-RUN echo "deb http://deb.debian.org/debian experimental main" > /etc/apt/sources.list.d/experimental.list && \
-    apt-get update && \
+RUN apt-get update && \
     apt-get install -y --no-install-recommends \
         apt-transport-https \
         binfmt-support \
@@ -81,6 +80,8 @@ RUN echo "deb http://deb.debian.org/debian experimental main" > /etc/apt/sources
         openssh-client \
         parted \
         pkg-config \
+        qemu-system-x86 \
+        qemu-user-static \
         rsync \
         systemd \
         systemd-container \
@@ -90,9 +91,6 @@ RUN echo "deb http://deb.debian.org/debian experimental main" > /etc/apt/sources
         xfsprogs \
         xz-utils \
         zip && \
-    apt-get install -y --no-install-recommends -t experimental \
-        qemu-system-x86 \
-        qemu-user-static && \
     rm -rf /var/lib/apt/lists/*
 
 # debian's qemu-user-static package no longer registers binfmts